Conventional utility knifes are generally designed to fix a blade onto a blade sliding seat so as to allow the blade to be extendable out of a shell of the utility knife or retractable back in the shell via moving of the blade sliding seat.
However, conventional utility knifes can only be equipped with one blade for use. When the blade in use becomes worn out and dull during its use process or different blades are required for use, it is necessary to firstly dismantle the originally installed blade from the blade sliding seat and replace it with another blade. It is rather inconvenient for use.
Furthermore, it is rather inconvenient and time-consuming to replace different blades in the abovementioned way when continuously and alternately using different types of blades is necessary for accomplishment of any particular work content. Generally speaking, under such circumstances, two or more utility knifes are prepared to perform such work content for the sake of saving time. However, such working manner further causes problems of inconvenient carrying and being costly, etc.
Accordingly, it is necessary to invent improved products to overcome the above-mentioned shortcomings and problems.